Noise in nonreciprocal two ports based on Hall effect

The noise behavior of four-terminal Hall-effect elements with
R_{12} = -R_{21}
is discussed. In the case of purely thermal noise, the noise sources at the input and output are uncorrelated. The noise figure is calculated, and a relationship between maximum available gain and noise figure is found if
R_{11} = R_{22}
. The smallest noise figure which may be achieved is 7.66 db. The final section of the paper discusses the influence of current noise. It is shown that "white" current noise can be neglected with respect to thermal noise in InAs and InSb. Measurements of flicker noise are given. High frequency behavior is discussed.